1. Field of the Invention
The present invention relates to a riding-type lawn mower with a rear discharge slot, and more particularly to a riding-type lawn mower having two horizontally rotatable cutter blades that are juxtaposed laterally with respect to each other and housed in a cutter housing which has a discharge slot defined in a rear wall thereof and is disposed substantially centrally below the body of the lawn mower.
2. Description of the Prior Art
Some known walking-type lawn mowers have two horizontally rotatable cutter blades that are juxtaposed laterally with respect to each other and housed in a cutter housing which has at least one rearwardly opening discharge slot. The cutter blade which is positioned on the right-hand side as viewed in the forward direction of the lawn mower is rotatable counterclockwise when viewed in plan. Such lawn mowers are disclosed in U.S. Pat. No. 3,157,014 and Japanese Laid-Open Patent Publication No. 58-129907.
The cutter housing shown in U.S. Pat. No. 3,157,014 has two laterally spaced independent discharge slots defined in the rear wall thereof. In the lawn mower disclosed in Japanese Laid-Open Patent Publication No. 58-129907, the cutter housing has a common discharge slot defined in a rear wall thereof and divided into two laterally spaced openings by a partition, and also has an upper wall whose laterally spaced outer portions are progressively higher toward the discharge slot, with motors mounted on the upper wall and connected to the respective cutter blade assemblies.
FIG. 5 of the accompanying drawings shows the manner in which grass is clipped by such a conventional lawn mower. It is assumed that the grass is cut by two laterally spaced cutter blades b housed in a cutter housing h as the lawn mower moves in a forward direction indicated by the arrow F. When the lawn mower moves, two strips of grass are trampled on forwardly by two front wheels f of the lawn mower, as shown in FIG. 6, and thereafter the grass is cut by cutting edges c of the cutter blades b.
As shown in FIG. 7, if the cutting edges c of each cutter blade b traveled in a direction r, which would be the same as the forward direction F, in the trampled-on grass strip, then the trampled-on grass would be further pressed downwardly by the cutting edges c and air streams developed thereby. If the cutter blades b are rotated to move the cutting edges c in a direction R, which is opposite to the forward direction F, in the trampled-on grass strip, then the trampled-on grass can be raised by the cutting edges c and air streams developed thereby. Since the raised grass can effectively be cut off by the cutting edges c, the grass can be clipped well.
Therefore, it is preferable, as shown in FIG. 5, that the cutter blade b positioned on the righthand side as viewed in the forward direction F be rotated clockwise as viewed in plan, and the cutter blade b positioned on the lefthand side as viewed in the forward direction F be rotated counterclockwise as viewed in plan.
With the cutter blades rotating in the above directions, the cutter housing should have separate grass clipping passages connected to the cutter blades b, the grass clipping passages being defined by the laterally spaced portions of the upper wall of the cutter housing that are progressively higher toward the rear discharge slots.
In riding-type lawn mowers, unlike the disclosed walking-type lawn mowers, it is necessary that the rotative power from the engine mounted on the body of the lawn mower be transmitted to two rotatable shafts coupled to the cutter blades and projecting upwardly from the cutter housing. Since the cutter housing is vertically movable for adjusting the height of trimmed grass, the engine is usually coupled to the rotatable shafts of the cutter blades through a belt-and-pulley mechanism.
Because the belt-and-pulley mechanism is disposed on the progressively higher portions of the upper wall of the cutter housing, the overall height and hence the overall size of such a riding-type lawn mower are larger than those of conventional riding-type lawn mowers.